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Growing Leeks

Posted: March 10, 2015

Consider adding leeks to your spring vegetable garden. Leeks look like large scallions, having slightly enlarged lower stems and upright leaves, which are flat and thick, unlike onions’ tubular leaves. They are milder than onions and have a distinctive, though similar, flavor. Leeks are delicious additions to soups and stews. They can also be added to stuffing, gratins, and casseroles, or sautéed with other vegetables such as carrots.
Prize winning leeks at the PA Farm Show

Prize winning leeks at the PA Farm Show

Leeks should be planted in April, once the soil has dried and warmed. If you start them indoors from seed, the seeds must be sown 6 to 8 weeks prior to the transplanting date.

Like most vegetables, leeks prefer full sun and a slightly acidic soil (pH of 5.5 to 7.0) which is well-drained and rich in organic matter. Because the white portion of the stem is what is used in cooking, leeks should be planted deeply to promote blanching. Soil can also be “hilled” around the lower portion of leeks as they grow to shield the stem from becoming green, which occurs when it is exposed to the sun. Some gardeners plant leeks in a trench and then add soil as the leeks grow to ensure a longer white stem.

I’m always looking for easier ways to garden, and over the years I’ve discovered a quicker, less labor-intensive way to plant leeks in my raised beds. After preparing the soil, I mark off rows about a foot apart. I then use a garden fork to carefully create deep holes along the row. I then put the leeks in alternate holes to allow sufficient space (about 4 inches) between plants, leaving just the very top portion of the leaves above ground to blanch the lower stem.

Monitor the leek bed to ensure adequate moisture throughout the growing season. Watering at soil level with a soaker hose is preferable to overhead watering, which can promote fungal disease. Add mulch to retain soil moisture and control weeds.

Leeks are susceptible to the same diseases as onions. Use a preventive fungicide if you have experienced problems growing onions in your garden. They should also be monitored for onion pests such as leaf miners and thrips. A 3 to 4 year crop rotation schedule will help to control disease and insect problems.

leeksUnlike onions, leeks do not fall over when they are ready for harvest. They can be harvested when the stem reaches 1 inch in diameter, or allowed to remain until they become somewhat larger. When harvesting, do not attempt to simply pull out the deeply planted leeks or they may break off. Instead, insert a digging fork and lift them out, being careful not to damage the leeks as you dig.

Usually only the stem portion of leeks is eaten because the leaves are tough. Many people use only the white part of the stem, but the lighter green portion may also be used. Leeks keep in the refrigerator for several days and may be frozen.

Leeks are not readily available in garden centers, but both seeds and plants may be purchased from gardening catalogs or the Internet.  

If you like leeks, growing your own will provide a bountiful harvest of quality vegetables at minimal cost.

Mary Ann Miller, Luzerne County Master Gardener